The V8 engine (not sure about the V6) has an auxiliary water pump (electric) that is controlled by the A/C module. Does anybody know the function of this pump and the circumstances when it is switched in?

 

Yes it is only on the V-8 engine. Not completely sure on its function but the main symptom when it fails is no heat at idle. At higher engine speeds the regular water pump is enough but at idle the flow drops and the AUX pump may be turned on.
.
.
.

 

The pump turns on and actually runs the entire time that one of the DCCV valves is open. Basically when you select heat, the pump is running, it adds more pressure to speed up flow throught the heater cores. The pump doesn't turn on or off depending on engine speed. (It would act as a restriction to the mechanical water pump).

When the heat is off there is no flow to the pump anyway because the coolant is stopped by the DCCV.

Take care,

George

 

Thanks guys - my car is actually a diesel which I know you don't have over there but it also has the auxiliary coolant pump fitted.

The reason for my interest is that it also has a Webasto fuel burning heater that operates below 5 degC when the engine is running. I am looking into whether it can be made to run without the engine to warm things through before starting on cold mornings.

There would need to be water circulation when it operates and this pump hopefully will do that for me.

 

Thanks for the information. Did not know the diesel had the AUX pump too? I wonder if it's operation is the same as the 4.2 L V-8?? I bet you would get heat pretty fast by burning fuel!!
.
.
.

 

Is that from the Factory or is this an aftermarket add on for cars that live in cold climates??

George

 

The Webasto unit is fitted to all S-Type diesels. The diesel engines do not generate the same level of heat as the gas units and in cold weather there simply isn't enough heat to get the engine up to temperature and to warm the cabin.

Many European diesel cars have this system and in some cases (not in the Jag) the unit can be switched by a timer or remote control to heat the car before starting in the morning. The most sophisticated of them work in conjunction with the Climate Control system and switch the internal blowers on too - so the car is toasty warm when you get in!

 

Hi there,

Sorry to revive an old thread but I've just discovered the auxilliary heater in the manual for the 2.7D and am looking at whether it is usable with the Webasto Thermo Top V in a parking heater configuration. Did you get any further with this?

I've sourced a Land Rover circulation pump, but haven't determined where to install it yet and would rather use the existing pump if possible. If the pump is driven by 12V directly, rather than a PWM signal, then in theory, it should work.

Thanks,
Toby

 

The UK forum has lengthy threads including how to do all manner of things and wire up to it. There are no S-Type diesels in USA etc so you'll struggle on here.

 

Yes, I appreciate that the diesel variant didn't make it to the USA but since the OP raised the original question on this site, I decided to respond here.

Is far as I'm aware, this hasn't been done before - I've found no mention of it on the UK forum.

 

The details of hooking up to a computer to control it were. Quite a good start maybe. The OP is about a pump not fitted to any but the V8. Nothing at all to do with the Webasto or diesel. Only the D has the aux heater.

 

Hi there,

The OP goes on to explain his interest is in using the auxiliary pump (which is also fitted to the diesel) to circulate coolant whilst the Webasto heater is running with the engine switched off (parking heater mode).

I've had the heater plugged into a laptop for diagnostics and testing and am now looking to take the next step and run the heater with the engine off (it quickly reaches temperature and switches off without coolant circulating).

JagV8 - you seem to think that my posts are off topic. Surely some useful information might come of a discussion about this pump, how it functions, fails, how to access it to repair/replace it etc. This might even have some relevence for the V8 engine if they share the same part.

 

Well, anything's possible they do say. The V8 one is quite well known on here and pretty unexceptional as I would hope you've read.

 

Hi Toby



Unfortunately, I did not manage to crack this problem on my car.



The Webasto unit itself is controlled by the can-bus (is that pwm?) and depends on a signal being sent from the aircon module to the unit when the ambient temperature is less than 5 deg C. To control this manually it is necessary to employ a device that can also produce this signal. Webasto produce a timer unit which can be bought for around £50 which will do this and then at least you could selectively switch the unit at any temperature.



I did not find any more information regarding the circulation pump so did not pursue any further. If you have a circulation pump from a LR and connect this to the Webasto then it should operate with the unit and provide the circulation required so a remote switch or timer could then be used. Getting the interior fans to operate however would be another thing!



I wish you luck with it, i have had to content myself with the abilty to diagnose problems and at least have a working unit that operates as it was designed.



Out of interest, I also have a Rover 75 with a Webasto unit and that was very easy to install a switch in the cabin to operate the unit whenever I choose. (simply needs a -ve supply to the diagnostic pin!)


Howard

 

Hi Howard,

Thanks for the information, I thought that might have been the case as there was no follow up.

I've got a 1533 timer on order to handle switching the heater on and off - should have that wired up in the next week or two. This will be a major improvement as I think the <5°C operation is a bit on the low side and will probably use it when the temperature is <10°C to reduce the warm up time (and engine wear).

I'm trying to determine whether the auxiliary pump fitted to the diesel is supplied with 12V or a PWM (Pulse Width Modulated) signal. The latter is still 12V but at varying duty cycles (ratio of 'on' to 'off') used to control the speed of the motor. I suspect that it is simply supplied with 12V via a relay (seems that the V8 pump works this way). I was working on my car yesterday and could hear a pump running after I switched the engine off, so perhaps they perform a similar function in both engine configurations. If the pump is simply supplied with 12V then I don't see why a remote channel couldn't be connected to energise the relay when using the heater in parking mode. The other concerns are the configuration of the heater valves and coolant path when the car is 'asleep'.

I purchased my S-type after owning a Rover 75 (where else can you go after 75 ownership!). I fitted a Thermo Top Z to that car and retrofitted a circulation pump and remote control. This was a great system and easy to control by grounding one of the pins as you mentioned. I guess I'm looking to get as close to that setup with the TT-V fitted to the S-type as possible. I never configured the interior fans on the Rover, but found that preheating the coolant on a cold morning and then a quick blast of the fans (with the key in the ignition) was sufficient.

Cheers,
Toby

 

Okay, so the electrical guide for the 2004 model states that the auxiliary pump was only fitted to the 4.2L petrol. However, the workshop manual shows the pump in the engine cooling system diagram. I'm pretty sure I can see the pump on my car and it is fitted with relay R7 in the front fuse box (which is designated for the auxiliary pump).

I think I'll have a play with the relay and see if I can get the pump running. If so, I'll test it with the heater running and engine off and see if it produces sufficient coolant flow to prevent the heater from shutting down due to reaching it target temperature.

 

I believe the V8 aux coolant pump does not run after you switch the engine off so that would be another difference. You should be able to run the 2.7D's pump via a relay. (I'd be worried about battery drain.)

The UK site seemed to say the Webasto is ISO (9141) but I think that may be what was added rather than the way Jag wire it from the factory (the D's elec guide shows it as CAN).

 

I got the auxiliary pump running tonight by removing the relay (R7) and connnecting a multimeter set to measure current (10A) between the sockets for pin 5 and 3. The pump was drawing ~0.9A which puts the power consumption at ~11W. Webasto specs two types of circulation pump for the Thermo Top V, a 12W version with a flow rate of 500l/h and a 13.9W version with a flow rate of 450l/h. I was unable to find any specs on the auxiliary pump fitted to the diesel but the power consumption seems to be comparable and hopefully the flow rate will be sufficient for a parking heater configuration.

I then fired up the heater and kept the pump running for a couple of minutes, the temperature increased at a steady rate. I left it running till the coolant reached 60°C and then switched the pump off. The heater quickly reached 87°C (and burn out). More testing required but it looks like this may be a viable configuration for a parking heater!

 

For the pump control during parking heater mode, I'll add another relay in OR configuration (see attached). Either the ACCM or the remote control/timer output can provide 12V to the auxiliary pump.

 

Hi Toby

It seems you are making real progress with this and I will be very interested to hear if you succeed with the timer. The only mention of the auxiliary pump that I could find said it was a new brushless pump "for durability and reliability". No further technical info.

best wishes

Howard